This book, now re-issued with a new introduction by Mary Boyce, is the first attempt to trace the continuous history of the faith from the time it was preached by Zoroaster down to the present day-a span of about 3,500 years. First taught among nomads on the Asian steppes, Zoroastrianism became the state religion of the three great Iranian empires. With the conquest of Iran by the Muslim Arabs, Zoroastrianism lost its secular power but continues to survive as a minority faith.